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Date:   Wed, 17 Mar 2021 15:10:52 +0100
From:   Sascha Hauer <s.hauer@pengutronix.de>
To:     dillon min <dillon.minfei@gmail.com>
Cc:     Rob Herring <robh+dt@kernel.org>, shawnguo@kernel.org,
        parthiban@linumiz.com, kernel@pengutronix.de, festevam@gmail.com,
        linux-imx@nxp.com,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] ARM: dts: imx6ull: fix ubi mount failed on MYS-6ULX-IOT
 board
Message-ID: <20210317141052.GW4207@pengutronix.de>
References: <1615270520-16951-1-git-send-email-dillon.minfei@gmail.com>
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 <CAL9mu0JOyM8n9LABwrOYgV4Qxj27XKTchWiGKsE3dMU0W5RNbw@mail.gmail.com>
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On Wed, Mar 10, 2021 at 10:54:05AM +0800, dillon min wrote:
> Hi Sascha,
> 
> Thanks for reviewing.
> 
> On Tue, Mar 9, 2021 at 8:18 PM Sascha Hauer <s.hauer@pengutronix.de> wrote:
> >
> > On Tue, Mar 09, 2021 at 02:15:19PM +0800, dillon.minfei@gmail.com wrote:
> > > From: dillon min <dillon.minfei@gmail.com>
> > >
> > > This patch intend to fix ubi filesystem mount failed on MYS-6ULX-IOT board,
> > > from Micron MT29F2G08ABAEAWP's datasheets, we need to choose 4-bit ECC.
> > >
> > > Table 18: Error Management Details
> > >
> > > Description                                   Requirement
> > >
> > > Minimum number of valid blocks (NVB) per LUN  2008
> > > Total available blocks per LUN                        2048
> > > First spare area location                     x8: byte 2048 x16: word 1024
> > > Bad-block mark                                        x8: 00h x16: 0000h
> > > Minimum required ECC                          4-bit ECC per 528 bytes
> > > Minimum ECC with internal ECC enabled         4-bit ECC per 516 bytes (user data) + 8
> > >                                               bytes (parity data)
> > > Minimum required ECC for block 0 if PROGRAM/
> > > ERASE cycles are less than 1000                       1-bit ECC per 528 bytes
> >
> > 4-bit ECC is the minimum this chip requires. There's nothing wrong with
> > choosing a better ECC like the GPMI driver does by default.
> >
> Yes, indeed, the mt29f2g08's minimum ecc is 4-bit, you can use 8-bits ecc.
> but there is a dependency between new kernel gpmi-nand with the old
> mfg-kernel's , which means
> if the old nand ecc layout is 4-bits, you should use ecc 4-bit in the
> new kernel (by fsl,use-minimum-ecc),
> else use 8-bits.
> 
> For my case, the ubifs filesystem was created by ecc 4-bits, without
> reflash filesystem or change

Then this is the justification for this patch, not anything from the
datasheet like you've written in your commit message.

Sascha

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